What happens to wine grapes?

What happens to wine grapes once they are picked? These red wine grapes are Pinot Noir grapes in half-ton bins.  This is the wine cellar of Marimar Torres winery in the Green Valley AVA of Sonoma. These grapes will all be crushed and their juice and skins will be poured into the stainless steel fermenting tanks you see in the photo. Some winemakers will stick with the native yeast on the skin of the grapes, and other winemakers will use special yeasts. The job of the yeast is to eat the sugars in the grape juice and reproduce. When the yeast eats the sugar, two important things happen. Alcohol is made and carbon dioxide released. It takes several days for fermentation to complete. When all the sugar is consumed, the yeast cells die and fermentation ends. While fermentation is taking place, it is very important for the skins and wine juice to be mixed. This is called the “punch down.” A mass of the grape skins comes to the top and is called the “cap.” The “cap” must be pushed down. It can be done by hand or by machine. I have tried the punch down myself a couple of times. It looks easy but the “punch down” is a workout. Small wineries are likely to do this by hand and larger wineries mechanically. When fermentation is done, the juice is filtered into aging vessels. The most common way to age the wine is in 60-gallon oak barrels. Aging goes on from 6 months to up to 2 years, depending on the quality of the grape juice. Once the wine is aged, it is bottled. The wine bottles will sit in the winery for several months before being released. If you are lucky enough on a winery tour, you will be able to watch a bottling line. It is very educational to watch the wine pour into the bottle, the bottle corked, the label placed on the bottle, and finally packaged into cases. White wine is made slightly differently,  so we will visit that in another article on winemaking.

More on how wine is made